Response of Ricinus communis L. to in vitro water stress induced by polyethylene glycol

Two castor bean cultivars were subjected to water stress induced by polyethylene glycol 6000 (PEG) under in vitro conditions. After 15 days, a reduced percentage of surviving plants, leaf abscission and greater leaf cuticular wax content were observed, accompanied by reduced water loss through the leaves. PEG also caused a decrease in soluble protein content and increases in the levels of hydrogen peroxide (H2O2) and malondialdehyde, as well as increases in the specific activities of superoxide dismutase, ascorbate peroxidase and catalase enzymes. These findings suggest that the mechanisms of tolerance of these genotypes are associated with their ability to activate key enzymes of the antioxidant defense system. However, the adaptive responses induced in response to stress were not sufficient to improve plant performance during the acclimatization period, and their survival rate dropped nearly 50 % relative to control treatment.